But shouldn't you rather take into account the tolerances of pregnant women and people younger than the age when one can be trained? If they can't live on the planet, it can't be colonized.
I'm not an expert in diving (I only dived once about 10m deep during holidays), but AFAIK the training (and the trouble) is mostly to handle the change in pressure, much more than the high pressure itself. Going from 1Am to 10Am is dangerous if done without respecting many safety measures, but once you're adjusted at 10Am, it's not so much a problem. So a child born on higher pressure wouldn't have too much troubles. Maybe 10Am is too much, but I don't think 1.5Am or 2Am would cause any serious trouble, if the composition of the atmosphere is good enough.
There's a lot of background mess in our mental pictures of the world. We try and be accurate on important issues, but a whole lot of the less important stuff we pick up from the media, the movies, and random impressions. And once these impressions are in our mental pictures, they just don't go away - until we find a fact that causes us to say "huh", and reassess.
Here are three facts that have caused that "huh" in me, recently, and completely rearranged minor parts of my mental map. I'm sharing them here, because that experience is a valuable one.